The present invention relates to an apparatus for operating at least one light-emitting diode.
By nature, light-emitting diodes need to be supplied with direct current. It is thus not possible for light-emitting diodes to be directly operated from voltage sources. In practice, therefore, light-emitting diodes are operated using matched DC supply circuits.
In some areas of use for light-emitting diodes, for example in the furniture sector, halogen lamps are also used for illumination purposes in addition to light-emitting diodes for special effects. Unlike light-emitting diodes, halogen lamps are operated from high-frequency voltage sources. The prior art therefore uses a separate drive circuit for the light-emitting diodes and a separate drive circuit for the halogen lamps.
The present invention sets itself the object of proposing an implementation which is more economical than that in the prior art and is particularly distinguished by a low level of installation complexity.
To achieve this object, the invention proposes that the output of the electronic transformer contained in the drive circuit for a halogen lamp have a high-frequency rectifier connected to it whose output is then coupled to the at least one light-emitting diode, the high-frequency rectifier and the at least one light-emitting diode being combined to form a separate physical unit.
This measure enables the transformer which needs to be provided in the drive circuit for the at least one light-emitting diode in the prior art to be dispensed with. In respect of the fact that the dimensional design of the transformer for driving the at least one light-emitting diode needs to be geared to mains frequency, the present case affords a considerable saving in terms of cost and space. The electronic transformer provided in the drive circuit for the halogen lamp usually comprises, first, a mains rectifier followed by a high-frequency inverter which is in turn connected to a transformer. Since the transformer is designed for high frequency, this component is much smaller than the transformer in the drive circuit for the at least one light-emitting diode in the prior art.
Since the output signal from the electronic transformer is not suitable for driving at least one light-emitting diode, rectification is performed. The combination of the high-frequency rectifier and the at least one light-emitting diode to form a separate physical unit, in accordance with the solution according to the invention, considerably simplifies the level of installation complexity, since the connection between the high-frequency rectifier and the light-emitting diode is already in place, and installation merely requires that this separate unit be connected to the output of the electronic transformer.
To this extent, the solution according to the invention also consists in providing an apparatus which comprises a high-frequency rectifier and at least one light-emitting diode, the high-frequency rectifier and the at least one light-emitting diode being combined to form a separate physical unit.
With particular advantage, the high-frequency rectifier is in this case arranged in the light-emitting housing of the at least one light-emitting diode, and provision may be made for the high-frequency rectifier and the at least one light-emitting diode to be arranged on a single circuit board. Accommodation in a common housing reduces the manufacturing complexity for such combinations, which has an associated reduction in cost.
The high-frequency rectifier may be in the form of a half-wave rectifier or a full-wave rectifier. With particular advantage, the high-frequency rectifier comprises a smoothing circuit.
In terms of the current limiting required for operating light-emitting diodes, two types of implementation may be provided: on the one hand, at least one series circuit comprising at least one series resistor and at least one light-emitting diode is arranged at the output of the high-frequency rectifier, and on the other hand at least one impedance, in particular at least one inductor, is provided at the output of the electronic transformer. In terms of the latter implementation, it is particularly advantageous for the impedance to be realized by the high-frequency rectifier. For this purpose, particularly advantageous high-frequency rectifiers can be found in patent application GR 99 P 5556 DE, inventor Felix Franck, entitled xe2x80x9cGleichrichter mit Mittelpunkteinspeisungxe2x80x9d [Rectifier with midpoint feed].
Further advantageous developments of the invention are defined in the dependent claims.